RESUMO
Genetic susceptibility to type 2 diabetes involves many genes, most of which are still unknown. The lipid phosphatase SHIP2 is a potent negative regulator of insulin signaling and sensitivity in vivo and is thus a good candidate gene. Here we report the presence of SHIP2 gene mutations associated with type 2 diabetes in rats and humans. The R1142C mutation specifically identified in Goto-Kakizaki (GK) and spontaneously hypertensive rat strains disrupts a potential class II ligand for Src homology (SH)-3 domain and slightly impairs insulin signaling in cell culture. In humans, a deletion identified in the SHIP2 3' untranslated region (UTR) of type 2 diabetic subjects includes a motif implicated in the control of protein synthesis. In cell culture, the deletion results in reporter messenger RNA and protein overexpression. Finally, genotyping of a cohort of type 2 diabetic and control subjects showed a significant association between the deletion and type 2 diabetes. Altogether, our results show that mutations in the SHIP2 gene contribute to the genetic susceptibility to type 2 diabetes in rats and humans.
Assuntos
Mapeamento Cromossômico , Diabetes Mellitus Tipo 2/genética , Monoéster Fosfórico Hidrolases/genética , Regiões 3' não Traduzidas/genética , Animais , Sequência de Bases , Células CHO , Linhagem Celular , Estudos de Coortes , Cricetinae , Diabetes Mellitus Tipo 2/enzimologia , Amplificação de Genes , Genes Reporter , Genótipo , Humanos , Hibridização in Situ Fluorescente , Rim/embriologia , Rim/enzimologia , Luciferases/genética , Camundongos , Dados de Sequência Molecular , Fosfatidilinositol-3,4,5-Trifosfato 5-Fosfatases , Monoéster Fosfórico Hidrolases/metabolismo , Ratos , Proteínas Recombinantes/metabolismo , Valores de Referência , Deleção de Sequência , Transfecção , Domínios de Homologia de src/genéticaRESUMO
Type II SH2 domain-containing inositol 5-phosphatase (INPPL1, or SHIP2) plays an important role in the control of insulin sensitivity. INPPL1 mutations affecting gene function have been found in rat models of type 2 diabetes and hypertension and in type 2 diabetic patients. We investigated the influence of nucleotide variation in INPPL1 on components of the metabolic syndrome. Following comprehensive resequencing of the gene, we genotyped 12 informative polymorphisms in 1,304 individuals from 424 British type 2 diabetes families that were characterized for several metabolic phenotypes. We have found highly significant associations of single nucleotide polymorphisms (SNPs) and haplotypes of INPPL1 with hypertension as well as with other components of the metabolic syndrome. In a cohort of 905 French type 2 diabetic patients, we found evidence of association of INPPL1 SNPs with the presence of hypertension. We conclude that INPPL1 variants may impact susceptibility to disease and/or to subphenotypes involved in the metabolic syndrome in some diabetic patients.
Assuntos
Síndrome Metabólica/fisiopatologia , Monoéster Fosfórico Hidrolases/genética , Polimorfismo Genético , Domínios de Homologia de src/genética , Idoso , Animais , Estudos de Coortes , Diabetes Mellitus Tipo 2/genética , Feminino , Genótipo , Haplótipos , Humanos , Hipertensão/genética , Masculino , Síndrome Metabólica/genética , Pessoa de Meia-Idade , Dados de Sequência Molecular , Fosfatidilinositol-3,4,5-Trifosfato 5-Fosfatases , Polimorfismo de Nucleotídeo Único , RatosRESUMO
Src homology domain 2-containing inositol 5-phosphatases 1 and 2 (SHIP1 and SHIP2) are capable of dephosphorylating the second messenger PtdIns(3,4,5) P3 (phosphatidylinositol 3,4,5-trisphosphate) and interacting with several signalling proteins. SHIP1 is essentially expressed in haematopoietic cells, whereas SHIP2, a closely related enzyme, is ubiquitous. In the present study, we show that SHIP1 and SHIP2 are expressed as functional PtdIns(3,4,5) P3 5-phosphatases in human blood platelets and are capable of interacting when these two lipid phosphatases are co-expressed, either naturally (platelets and A20 B lymphoma cells) or artificially (COS-7 cells). Using COS-7 cells transfected with deletion mutants of SHIP2, we demonstrate that the Src homology domain 2 of SHIP2 is the minimal and sufficient protein motif responsible for the interaction between the two phosphatases. These results prompted us to investigate the relative importance of SHIP1 and SHIP2 in the control of PtdIns(3,4,5) P3 levels in platelets using homozygous or heterozygous SHIP1- or SHIP2-deficient mice. Our results strongly suggest that SHIP1, rather than SHIP2, plays a major role in controlling PtdIns(3,4,5) P3 levels in response to thrombin or collagen activation of mouse blood platelets.